Cartilage • Specialized dense connective tissue • Semi rigid ,designed to give support, bear

weight & withstand tension ,torsion & bending • Devoid of blood vessels and not innervated

by nerve • Most of them are calcified in old age. • Cartilage can grow by interstitial &

appositional growth

Composition of cartilage

• Perichondrium • Ground substance-Highly hydrated Contains hyaluronic

acid glucoseaminoglycans • Cells- chondroblasts,

chondrocytes • Fibers- collagen , elastic fibers

Types of cartilage • Hyaline cartilage • Elastic cartilage • Fibrous cartilage

Hyaline cartilage • Most common type • Makes the skeletal

model of most bones in embryo

• Gradually replaced by bone in grown ups except at the articular surface of bones, ends of the ribs, nose, larynx, trachea and bronchi

• In living conditions looks translucent & bluish white in colour

• Covered with perichondrium. Articular cartilage is not covered by perichondrium

• Matrix is homogenous which consists of chondroitin sulphate & collagen fibers

• Cells are chondrocytes arranged in groups in lacunae • Collagen fibers are not visible in matrix because of the

same refractive index as that of matrix

Elastic cartilage • Present in external ear,

epiglottis, auditory tube & few cartilage of larynx

• Covered with perichondrium

• Number of cells are more • Matrix consist of bundles

of branching & anastomosing elastic fibers which give elasticity to the tissue

Fibrous cartilage • Found in intervertebral disc,

pubic symphysis, intrarticular disc of certain joints, menisci of knee joint & articular cartilage of temporomandibular cartilage

• Consists of bundles of collagen fibers embedded in minimal amount of matrix

• Cells are usually placed single in between the bundles of collagen fibers

• Not covered with perichondrium

BONE • Specializes form of dense

connective tissue • Makes supportive frame work • Support & transmit weight of

the body • Provide the levers for

locomotion by formingarticulations

• Give attachment to muscles & ligaments

• Provide mechanical protection to the vital organ

• Store calcium • Form blood in their marrow

Classification of bones According to position

Axial Appendiculer

Number of bones

• Total 206 bones • Upper limbs - 64 • Lower limbs – 62 • Vertebrae – 26(33) • Skull – 29(26Skull bones

+ hyoid +6 ossicle) • Ribs – 24 • Sternum

• Appendicular-Upper limb

Lower limb

64

62

• Long bones • Short bones • Short bones • Flat bones • Irregular bones • Pneumatic bones • Sesamoid bones • Accessory bones

According to size & shape

According to gross structure

• Compact (Lamellar) bone

• Spongy (cancellous) bone

• Diploic bones

According todevelopment

• Membranous bones-Bone is laid down directly in the fibrousmembrane e.g. bonesof vault of skull, mandible

• Cartilaginous bones-Formation of bone is proceeded by theformation of a cartilage,which is later replacedby a bone e.g. femur,tibia

Membranous ossification • Bone is formed in mesenchyme • The cells in mesenchyme secrete

ground substance & collagen fiber around themselves

• Thus ground substance, fiber & cells form a membrane

• Vascularization of membrane & differentiation of osteoblast cells

• Formation of osteoid matrix • Formation of calcified matrix • Formation of trabeculae, bone

cells (osteocytes) & lacunae • Subperiosteal ossification

Development Endochondral ossification • Condensation of mesenchymal

cells occur at the site of bone formation

• Mesen. Cells are transformed in to chondroblast which now form hyaline cartilage

• Formation of perichondrium which is highly vascular

• Hypertrophy of cartilage cells & formation of calcified matrix

• Subperiosteal ossification • Vascular invasion & osteogenesis

Composition of bone -• organic matter- forms 1/3 weight of bone.

Consists of fibrous material & cells. Responsible for toughness & resilience

• Inorganic matter- forms 2/3 weight of bone. Consists of mineral salts like calcium carbonate, cal. Fluoride, and magnesium phosphate Responsible for rigidity & hardness. Cal. In bone makes it opaque to x-ray

Macroscopic structure of living adult bone

• Compact bone • Cancellous bone

Microscopic structure of bone

Parts of a developing long bone • Diaphysis-

intermediate region or shaft

• Metaphysis-developing extraepiphyseal regions of shaft

• Epiphysis- ends of bone which ossify with a separate centre of ossifi. (secondary)

Epiphyseal cartilage • Zone of resting

cartilage • Zone of proliferating

cartilage • Zone of

hypertrophied cartilage

• Zone of calcified cartilage

Centers of ossification • Primary center • Secondary center • Epiphyseal line

Types of epiphysis Pressure epiphysis- articular & take part in

transmission of weight e.g. head of femur, lower end of radius

Traction epiphysis- Nonarticular & does not take part in the transmission of the weight.

• Tendons are attached here which exert a traction on the epiphysis

• Ossify later then the pressure epiphysis e.g. trochanters of tubercles of humerus

Atavistic epiphysis- femur, Phylogenetically an independent bone which in man become fused to another bone e.g. coracoid process of scapula & os trigonum

Aberrant epiphysis- Not always present e.g. epiphysis at the head of first metacarpal & at the base of other metacarpal bones

Blood supply of bone • Nutrient artery • Periosteal vessels • Metaphyseal vessels • Epiphyseal vessels

• Lymphatic supply- lymphatics present only in periosteum & Haversian system

• Accompany blood vessels • No lymphatic in the bone marrow • Lymphatic of the haversian system drain in to

periosteal vessels • Nerve supply- Most numerous at the articular

ends of the long bones vertebrae & flat bones • Distributed freely to the periosteum & with the

branches of nutrient artery. • Consist of both sensory & autonomic fibers

(blood vessels)

Some important points about ossification

• Ossification begins constantly at a prefixed spot & at a fairly constant time

• Centre may be primary or secondary • Primary center may be single or multiple

but appear & as a rule appear before birth • Between 6 to 8th wk of fetal life. Exception

cuneiform & navicular bones • Secondary center usually multiple &

appear after birth. Exception are lower end of femur

• Most long bones have epiphysis at both ends the epiphysis which ossifies first unites with the diaphysis last & the epiphysis which ossifies last fuses first. Exceptions. Lower end of fibula where epiphysis ossifies first, also fuses last with shaft

• The end of the long bone where epiphysis appear first & fuses last is called the growing end of the bone

• The direction of the nutrient artery is always away from the growing end of the bone given away by rhyme,

To the elbow I go, from the knee I flee”

• The different centers of ossification first unite together & then they unite with the shaft

• In long bones growing ends of the bone fuses with the shaft at about 20 years & the opposite end at about 18 years i.e. 2 years earlier

• Fusion of epiphysis with diaphysis occurs 2 years earlier in women than in men. Epiphysis also appear earlier in women

• Epiphysis in bones other than long bones fuses with main part of the bone between 20-25 years

Estimation of age, sex &height from the bones

• Timing of eruption of milk teeth & permanent teeth can estimate age up to18 years

• Age at which epiphysis of the bone appears and fuses with the diaphysis es fairlyconstant. This can provides the age till 25 years

• After 25 years age is estimated by the closing of cranial sutures &changes occuring at themedial surface of pubic bones. this age canbe estimated till 60 years

• Sex can be determined by studying morphological feature of the bone & the measurement of skull & pelvis

• Race can be determined with85-90% accuracy by metrical & nonmetrical data developed from cranial &other parts of skeleton.